Relationship between serum bilirubin and albuminuria in patients with type 2 diabetes

Bayesian analysis of joint quantile regression for multi-response longitudinal data with application to primary biliary cirrhosis sequential cohort study

This article proposes a Bayesian approach for jointly estimating marginal conditional quantiles of multi-response longitudinal data with multivariate mixed effects model. The multivariate asymmetric Laplace distribution is employed to construct the working likelihood of the considered model. Penalization priors on regression parameters are incorporated into the working likelihood to conduct Bayesian high-dimensional inference. Markov chain Monte Carlo algorithm is used to obtain the fully conditional posterior distributions of all parameters and latent variables. Monte Carlo simulations are conducted to evaluate the sample performance of the proposed joint quantile regression approach. Finally, we analyze a longitudinal medical dataset of the primary biliary cirrhosis sequential cohort study to illustrate the real application of the proposed modeling method.

Interplay of serum biomarkers bilirubin and γ-glutamyltranspeptidase in predicting cardiovascular complications in type-2 diabetes mellitus

This editorial synthesizes insights from a series of studies examining the interplay between metabolic and oxidative stress biomarkers in cardiovascular disease (CVD), focusing particularly on type-2 diabetes mellitus (T2DM) and acute coronary syndrome (ACS). The central piece of this synthesis is a study that investigates the balance between oxidative stress and antioxidant systems in the body through the analysis of serum bilirubin and γ-glutamyltranspeptidase (γ-GGT) levels in T2DM patients with ACS. This study highlights serum bilirubin as a protective antioxidant factor, while elevated γ-GGT levels indicate increased oxidative stress and correlate with major adverse cardiovascular events. Complementary to this, other research contributions reveal γ-GGT's role as a risk factor in ACS, its association with cardiovascular mortality in broader populations, and its link to metabolic syndrome, further elucidating the metabolic dysregulation in CVDs. The collective findings from these studies underscore the critical roles of γ-GGT and serum bilirubin in cardiovascular health, especially in the context of T2DM and ACS. By providing a balanced view of the body's oxidative and antioxidative mechanisms, these insights suggest potential pathways for targeted interventions and improved prognostic assessments in patients with T2DM and ACS. This synthesis not only corroborates the pivotal role of γ-GGT in cardiovascular pathology but also introduces the protective potential of antioxidants like bilirubin, illuminating the complex interplay between T2DM and heart disease. These studies collectively underscore the critical roles of serum bilirubin and γ-GGT as biomarkers in cardiovascular health, particularly in T2DM and ACS contexts, offering insights into the body's oxidative and antioxidative mechanisms. This synthesis of research supports the potential of these biomarkers in guiding therapeutic strategies and improving prognostic assessments for patients with T2DM and some CVD.

Precision subclassification of type 2 diabetes: a systematic review

BACKGROUND

Heterogeneity in type 2 diabetes presentation and progression suggests that precision medicine interventions could improve clinical outcomes. We undertook a systematic review to determine whether strategies to subclassify type 2 diabetes were associated with high quality evidence, reproducible results and improved outcomes for patients.

METHODS

We searched PubMed and Embase for publications that used 'simple subclassification' approaches using simple categorisation of clinical characteristics, or 'complex subclassification' approaches which used machine learning or 'omics approaches in people with established type 2 diabetes. We excluded other diabetes subtypes and those predicting incident type 2 diabetes. We assessed quality, reproducibility and clinical relevance of extracted full-text articles and qualitatively synthesised a summary of subclassification approaches.

RESULTS

Here we show data from 51 studies that demonstrate many simple stratification approaches, but none have been replicated and many are not associated with meaningful clinical outcomes. Complex stratification was reviewed in 62 studies and produced reproducible subtypes of type 2 diabetes that are associated with outcomes. Both approaches require a higher grade of evidence but support the premise that type 2 diabetes can be subclassified into clinically meaningful subtypes.

CONCLUSION

Critical next steps toward clinical implementation are to test whether subtypes exist in more diverse ancestries and whether tailoring interventions to subtypes will improve outcomes.

High-normal unconjugated bilirubin is associated with decreased risk of chronic kidney disease in type 2 diabetes: A real-world study

OBJECTIVE

To investigate the association between serum unconjugated bilirubin (UCB) within normal limits and chronic kidney disease (CKD) in T2DM patients.

METHOD

This cross-sectional, real-world study was performed in 8661 hospitalised T2DM patients. The subjects were stratified into quintiles based on serum UCB levels. The clinical characteristics and CKD prevalence were compared among the UCB quantile groups. The associations of serum UCB levels and quintiles with CKD were also analysed by binary logistic regression.

RESULTS

After controlling for age, sex, and diabetes duration (DD), the CKD prevalence (20.4%, 12.2%, 10.6%, 8.3%, and 6.4% for the first, second, third, fourth, and fifth quintiles, respectively, p < 0.001 for trend) was significantly decreased across the serum UCB quintiles. The fully adjusted regression model showed negative associations of serum UCB levels (OR: 0.660, 95% CI: 0.585-0.744; p < 0.001 for trend) and quintiles (p < 0.001) with the presence of CKD. Compared with the subjects in the lowest UCB quintile, the risk of CKD decreased by 36.2%, 54.3%, 53.8%, and 62.1%, respectively, in those from the second to the highest UCB quintile. Additionally, C-reactive protein (CRP) levels were significantly higher in the subjects with CKD than in those without CKD (p < 0.001), and significantly decreased across the UCB quintiles (p < 0.001 for trend).

CONCLUSIONS

Serum UCB levels within the normal range were significantly and negatively linked to CKD in T2DM patients. High-normal UCB may be an independent protective factor for CKD by its antioxidant and the following anti-inflammatory activities through its signalling activity, which was indicated by clearly decreased CRP levels across the UCB quintiles.

Systematic review of precision subclassification of type 2 diabetes

Heterogeneity in type 2 diabetes presentation, progression and treatment has the potential for precision medicine interventions that can enhance care and outcomes for affected individuals. We undertook a systematic review to ascertain whether strategies to subclassify type 2 diabetes are associated with improved clinical outcomes, show reproducibility and have high quality evidence. We reviewed publications that deployed 'simple subclassification' using clinical features, biomarkers, imaging or other routinely available parameters or 'complex subclassification' approaches that used machine learning and/or genomic data. We found that simple stratification approaches, for example, stratification based on age, body mass index or lipid profiles, had been widely used, but no strategy had been replicated and many lacked association with meaningful outcomes. Complex stratification using clustering of simple clinical data with and without genetic data did show reproducible subtypes of diabetes that had been associated with outcomes such as cardiovascular disease and/or mortality. Both approaches require a higher grade of evidence but support the premise that type 2 diabetes can be subclassified into meaningful groups. More studies are needed to test these subclassifications in more diverse ancestries and prove that they are amenable to interventions.

Bilirubin improves renal function by reversing the endoplasmic reticulum stress and inflammation in the kidneys of type 2 diabetic rats fed high-fat diet

Diabetic kidney disease (DKD), as a chronic diabetes-induced complication, is considered the most frequent leading cause of end-stage renal disease (ESRD). Regarding the observed protective effects of bilirubin, as a potential endogenous antioxidant/anti-inflammatory compound, against DKD progression, we planned to evaluate the effects of bilirubin administration on endoplasmic reticulum (ER) stress and inflammation in type 2 diabetic (T2D) rats fed high-fat diet (HFD). In this regard, thirty 8-week adult male Sprague Dawley rats were divided into five groups (n = 6). T2D and obesity were induced by streptozotocin (STZ) (35 mg/kg) and HFD (700 kcal/day), respectively. Bilirubin treatment was carried out for 6- and 14-week intervals (10 mg/kg/day), intraperitoneally. Then, the expression levels of ER stress-related genes (i.e. binding immunoglobulin protein (Bip), C/EBP homologous protein (Chop), and spliced x-box-binding protein 1 (sXbp1), as well as nuclear factor-κB (NF-κB) were analyzed using quantitative Real-time PCR experiments. Moreover, histopathological and stereological changes of kidney and its related structures were investigated for the studied rats. Bip, Chop, and NF-κB expression levels were significantly decreased under bilirubin treatment, while sXbp1 was up-regulated following the bilirubin administration. More interestingly, glomerular constructive damages seen in HFD-T2D rats, were considerably improved in the animals received bilirubin. Stereological assessments also revealed that bilirubin could desirably reverse the mitigation of kidney's total volume and its related structures, such as cortex, glomeruli, and convoluted tubules. Taken together, bilirubin has potential protective/ameliorative effects on DKD progression, especially through alleviating the renal ER stress and inflammatory responses in T2D rats with injured kidneys. In this era, clinical benefits of mild hyperbilirubinemia can be considered in human DKD.

Association of Serum Bilirubin Levels with Macro- and Microvascular Complications in Chinese People with Type 2 Diabetes Mellitus: New Insight on Gender Differences

Background

Previous studies suggested protective effects of bilirubin against cardiovascular disease, with a possible gender difference. However, the relationship between serum total bilirubin (TBIL) with diabetic macro- and microvascular complications remains unknown. We aimed to examine the association of macro- and microvascular complications with serum TBIL levels.

Methods

Serum TBIL was measured in 648 patients with T2DM. Demographic and clinical data were obtained from the inpatient medical record system. Serum TBIL was measured with an automatic biochemistry analyzer according to routine protocols. Parameters of vascular complications, including ankle-brachial index, carotid intima-media thickness, estimated glomerular filtration rate and the urinary albumin to creatinine ratio, were measured and calculated. The association between TBIL and diabetic macro- and microvascular complications was analyzed.

Results

In multivariable logistic regression, after adjustment for age, sex, body mass index and diabetic duration, higher serum TBIL levels were significantly associated with decreased odds of microalbuminuria (OR = 0.31, [95% CI] 0.16-0.61, P = 0.003) and chronic kidney disease (OR = 0.19, [95% CI] 0.09-0.41, P < 0.001). These associations were only found in male but not in female patients. However, no significant relationship was found between TBIL and peripheral arterial disease or carotid hypertrophy.

Conclusion

Our findings suggest that physiological higher TBIL level might be a protective factor for diabetic microvascular complications.

Serum bilirubin and kidney function: a Mendelian randomization study

Background

Further investigation is needed to determine the causal effects of serum bilirubin on the risk of chronic kidney disease (CKD).

Methods

This study is a Mendelian randomization (MR) analysis. Among the well-known single-nucleotide polymorphisms (SNPs) related to serum bilirubin levels, rs4149056 in the SLCO1B1 gene was selected as the genetic instrument for single-variant MR analysis, as it was found to be less related to possible confounders than other SNPs. The association between genetic predisposition for bilirubin levels and estimated glomerular filtration rate (eGFR) or CKD was assessed in 337 129 individuals of white British ancestry from the UK Biobank cohort. Two-sample MR based on summary-level data was also performed. SNPs related to total or direct bilirubin levels were collected from a previous genome-wide association study and confounder-associated SNPs were discarded. The independent CKDGen meta-analysis data for CKD were employed as the outcome summary statistics.

Results

The alleles of rs4149056 associated with higher bilirubin levels were associated with better kidney function in the UK Biobank data. In the summary-level MR, both of the genetically predicted total bilirubin {per 5 µmol/L increase; odds ratio [OR] 0.931 [95% confidence interval (CI) 0.871-0.995]} and direct bilirubin [per 1 µmol/L increase; OR 0.910 (95% CI 0.834-0.993)] levels were significantly associated with a lower risk of CKD, supported by the causal estimates from various MR sensitivity analyses.

Conclusion

Genetic predisposition for higher serum bilirubin levels is associated with better kidney function. This result suggests that higher serum bilirubin levels may have causal protective effects against kidney function impairment.

A simplified prediction model for end-stage kidney disease in patients with diabetes

This study aimed to develop a simplified model for predicting end-stage kidney disease (ESKD) in patients with diabetes. The cohort included 2549 individuals who were followed up at Kyushu University Hospital (Japan) between January 1, 2008 and December 31, 2018. The outcome was a composite of ESKD, defined as an eGFR < 15 mL min⁻¹ [1.73 m]⁻², dialysis, or renal transplantation. The mean follow-up was 5.6 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pm$$\end{document}± 3.7 years, and ESKD occurred in 176 (6.2%) individuals. Both a machine learning random forest model and a Cox proportional hazard model selected eGFR, proteinuria, hemoglobin A1c, serum albumin levels, and serum bilirubin levels in a descending order as the most important predictors among 20 baseline variables. A model using eGFR, proteinuria and hemoglobin A1c showed a relatively good performance in discrimination (C-statistic: 0.842) and calibration (Nam and D’Agostino \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\chi$$\end{document}χ² statistic: 22.4). Adding serum albumin and bilirubin levels to the model further improved it, and a model using 5 variables showed the best performance in the predictive ability (C-statistic: 0.895, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\chi$$\end{document}χ² statistic: 7.7). The accuracy of this model was validated in an external cohort (n = 5153). This novel simplified prediction model may be clinically useful for predicting ESKD in patients with diabetes.

Association of serum total bilirubin levels with progressive renal decline and end-stage kidney disease: 10-year observational cohort study in Japanese patients with diabetes

Objective

Previous reports have demonstrated the association of serum bilirubin levels with the progression of diabetic nephropathy. The objective of this study is to assess the association of basal bilirubin levels with progressive renal decline (PRD) and end-stage kidney disease (ESKD).

Methods

A total of 298 patients with diabetes who visited Kyushu University Hospital (Japan) were recruited and followed up for 10 years. PRD was defined as a negative change in estimated glomerular filtration ratio (eGFR) >3.7%/year, 2.5th percentile. Logistic regression analysis was performed to evaluate the association of total bilirubin levels with PRD and its cut-off point was determined by receiver operating characteristic (ROC) analysis. Kaplan-Meier method and Cox hazard regression analysis were used to evaluate the predictive ability of its cut-off point for ESKD.

Results

Logistic regression model showed that total bilirubin levels were significantly associated with PRD, and ROC analysis showed that its cut-off point was 0.5 mg/dL. Kaplan-Meier method showed that the percent of patients who reached two endpoints, composite endpoint (ESKD or doubling of creatinine level) or 30% eGFR decline, was significantly higher in the low bilirubin group than in the high bilirubin group (18.5% vs 11.0%, P = 0.045; 49.1% vs 42.1%, P = 0.045, respectively, log-rank test). Cox hazard regression models confirmed the independence of the predictive ability of its cut-off point.

Conclusions

Serum total bilirubin levels were negatively associated with PRD in diabetic nephropathy and its cut-off point was 0.5 mg/dL. It may be clinically useful for identifying patients at high risk of ESKD.

Exploring structural dynamics and optical properties of UnaG fluorescent protein upon N57 mutations

UnaG is a new class of fluorescence protein in which an endogenous ligand, namely bilirubin (BLR), plays the role of chromophore. Upon photoexcitation, holoUnaG emits green light. A single mutation at residue 57 induces a decrease in the fluorescence quantum yield. To our knowledge, no atomic simulation at the atomic level has been carried out to date to explain this fluorescence decay in N57A and N57Q mutants. Herein molecular dynamics simulations were carried out on wild-type (WT) UnaG and both mutants to investigate the structural impact of the mutation on its global structure, on BLR and the absorption spectra. Our study reveals significant global changes upon mutation at the protein entrance (L3, H2, and, H3) governing a BLR modification. BLR in WT UnaG is rather rigid while when embedded into N57A or N57Q, dihedral angles between endo and exo vinyl moieties and between A and B rings at the entrance of UnaG are strongly modified along with the number of inter-/intramolecular interactions. The water molecules play an important role in the modification of the shape of the binding cavity. For the first time, we show that the structural modifications upon ligand mutations are tightly related to the key structural changes in the protein such as Loop3 (L3), β sheet 2 (B2), and β sheet 3 (B3) dynamics. The present work suggests that the quenching of the fluorescence properties of UnaG mutants is mainly a non-radiative process closely related to the BLR flexibility induced by global structural changes.

Association of Serum Total Bilirubin and Uric Acid with Low Glomerular Filtration Rate Diabetic Kidney Disease in Type 2 Diabetic Patients

BACKGROUND

Diabetic kidney disease (DKD) is one of the major complications of Type 2 diabetes, clinically characterized by a progressive increase in albuminuria and/or a subsequent decline in glomerular filtration rate. Identification of novel risk factors contributes to reduction in the risk of diabetic kidney disease. Bilirubin, as an antioxidant and anti-inflammatory molecule, is believed to have a protective role in kidney disease. On the other hand, uric acid is implicated in the pathogenesis of DKD due to its pro-oxidant and pro-inflammatory property in vascular tissues.

METHODS

A hospital based comparative cross-sectional study was conducted from October 2020 to March 2021 on 200 eligible Type 2 diabetic patients (58 with DKD and 142 without DKD) to assess the association of serum total bilirubin and serum uric acid levels with low GFR diabetic kidney disease using consecutive sampling technique.

RESULTS

The serum total bilirubin level was significantly decreased (0.15±2.29, mean±SD) in the DKD group compared to the non-DKD group (0.19±2.26), whereas the mean±SD serum uric acid was significantly increased in the DKD group (7.13±2.21) compared to the non-DKD group (5.24±1.92). A low serum total bilirubin level was significantly associated with increased risk of DKD in multivariate analysis (AOR=2.23, 95% CI=1.55-4.13) also to high serum uric acid levels (AOR=2.09, 95% CI=1.06-4.12). Moreover, a low serum total bilirubin level was significantly associated with increased risk of DKD among patients with high serum uric acid (AOR=2.55, 95% CI=1.05-6.19). Similarly, high serum uric acid was significantly associated with increased risk of DKD among patients with low serum total bilirubin (AOR=3.49, 95% CI=1.29-9.42).

CONCLUSION

Co-presence of low serum total bilirubin and high serum uric acid may be useful for stratification of DKD risk among patients with Type 2 diabetes mellitus.

Bilirubin is inversely related to diabetic peripheral neuropathy assessed by sural nerve conduction study

AIMS/INTRODUCTION

Diagnosis of diabetic peripheral neuropathy (DPN) depends on subjective findings, certain investigations for DPN risks have not been performed enough. Bilirubin protects against vascular complications by reducing oxidative stress in diabetes, but is not fully tested for DPN. This study aimed to evaluate sural nerve conduction impairments (SNCI) as an objective DPN marker and the contribution of bilirubin to SNCI.

MATERIALS AND METHODS

Using DPN-Check® , SNCI was defined as a decline of amplitude potential or conduction velocity below the normal limit in 150 inpatients with diabetes. The correlations between SNCI and conventional DPN diagnosis criteria, the incidence of diabetic retinopathy/nephropathy, biomarkers for atherosclerosis, cardiac function by ultrasonic cardiogram, and bilirubin were statistically tested, followed by the comparison of logistic regression models for SNCI to find confounders with bilirubin.

RESULTS

The incidence of SNCI was 72.0%. The sensitivity and specificity of SNCI for DPN prediagnosis by simplified criteria were 54.6 and 90.5%, respectively, and similarly corresponded with diabetic retinopathy and nephropathy (sensitivity 57.4 and 50.0%, respectively). SNCI significantly related to diabetes duration, declined estimated glomerular filtration rate, albuminuria and total bilirubin. SNCI incidence was attenuated in the higher bilirubin tertiles (89.8/65.3/54.8%, P < 0.001). Bilirubin was an independent inverse risk factor for SNCI, even after adjustment by known risk factors for DPN and markers for microvascular complications.

CONCLUSIONS

SNCI is a comprehensive marker for diabetic complications. We first showed the independent inverse relationship between bilirubin and SNCI through the independent pathway with other complications, provably reducing oxidative stress, as previously reported.

Patients with Gilbert syndrome and type 2 diabetes have lower prevalence of microvascular complications

Objective

Accumulating clinical evidence indicates an inverse relationship between oxidative stress and unconjugated hyperbilirubinemia. This study aimed to compare the prevalence of diabetes microvascular complications in patients with Gilbert syndrome and type 2 diabetes mellitus (T2D).

Methods

A total of 1200 electronic records with T2D were reviewed. From them, 50 patients with Gilbert syndrome (cases [indirect bilirubin ≥1.2 mg/dl without evidence of hemolysis or liver disease]) and 50 controls (T2D without hyperbilirubinemia) were included. Linear and logistic regression models were performed to evaluate the independent association between indirect hyperbilirubinemia with microvascular complications related with T2D.

Results

Both case and control group had the same proportion of gender (female = 20 [40 %]) and diabetes duration (14.0 ± 6.5 years) and similar mean of age (60 ± 9.6 and 60 ± 9.2 years, respectively, p = 0.91). The median of unconjugated bilirubin of case and control group was 1.4 (1.2–1.6) vs. 0.4 (0.2–0.6) mg/dl (p < 0.001), respectively. Patients with elevated unconjugated bilirubin had less urine albumin-creatinine ratio compared with control group (8.5 [4.3–23] vs. 80 [8–408] mg/g, p < 0.001), and lower rate of diabetes microvascular complications and metabolic syndrome. After adjustment for BMI, age, HbA1c, blood pressure, triglycerides, and the metabolic syndrome, the lineal regression analysis showed that unconjugated bilirubin protects against microalbuminuria in T2D patients (β = −414.11, 95 % CI [-747.9, −80.3], p = 0.006. Also, unconjugated hyperbilirubinemia was independently associated with a better glomerular filtration rate (GFR) (β = 9.87, 95 % CI [1.5, 18.3], P = 0.02).

Conclusions

Patients with Gilbert syndrome and T2D had a lower prevalence of diabetes microvascular complications.

Serum Bilirubin Is Correlated With the Progression of IgA Vasculitis With Nephritis

Background: Bilirubin has been identified as an endogenous antioxidant and cellular protectant. The present study was performed to clarify the potential influence of serum bilirubin on IgA vasculitis with nephritis (IgAV-N). Methods: One hundred and eighty-nine IgAV-N patients over 14 years old were enrolled. The patients were divided into two groups by the optimum cut-off value calculated by ROC curve. The composite endpoints were defined as a 60% decline in estimate glomerular filtration rate (e-GFR), end-stage renal disease (ESRD) and/or death. Kaplan-Meier (K-M) analysis and multivariate Cox analysis were carried out to determine the predictors for renal outcomes. In order to eliminate the influence of different baseline data, a 1:2 propensity score (PS) match was performed to make the results comparable and convictive. Results: The baseline data suggested that patients in low serum bilirubin group had significantly higher levels of systolic blood pressure, proteinuria, serum creatinine and crescent formation ratio and lower levels of serum albumin and hemoglobin. Renal survival analysis indicated that lower serum bilirubin levels were significantly correlated with a poorer prognosis. Multivariate Cox analysis demonstrated that the higher level of serum bilirubin was an independent protective factor for renal survival (HR, 0.172; 95% CI, 0.030-0.991; P = 0.049). After PS matching, the baseline characters of two groups had no statistical differences. Similar outcomes were demonstrated in K-M curve and the multivariate Cox analysis. Conclusion: Elevated bilirubin levels might be related to the favorable renal outcomes.

Lower serum bilirubin is associated with poor renal outcome in IgA nephropathy patients

Aims: IgA nephropathy (IgAN) is the most prevalent primary glomerulonephritis worldwide. We conducted this study to explore the relationship between serum bilirubin and renal outcome of patients with IgAN. Methods: A total of 1492 biopsy proven IgAN patients were recruited and divided into two groups according to their median serum bilirubin concentration: the low bilirubin group (serum bilirubin≤9.7umol/L, n=753) and high bilirubin group (serum bilirubin>9.7umol/L, n=739). Basic clinical characteristics were assessed at the time of renal biopsy and the relationships between serum bilirubin and the combined endpoints were analyzed. The combined endpoints were defined as a 50% decline in estimate glomerular filtration rate (e-GFR), end-stage kidney disease (ESKD), renal transplantation and/or death. In addition, propensity score matching (PSM) was then performed to improve balance and simulate randomization between patients in different groups. Kaplan-Meier survival analysis was applied to explore the role of serum bilirubin in the progression of IgAN. Three clinicopathological models of multivariate Cox regression analysis were established to evaluate the association of serum bilirubin and renal prognosis of IgAN. Results: During median 5-year follow-up period, significant differences were shown in Kaplan-Meier analysis. In the unmatched group, 189 (12.7%) patients progressed to the renal combined endpoints. Among this, 122 in 753 patients (16.2%) were in low bilirubin group and 67 in 739 patients (9.1%) were in high bilirubin group (p<0.001). After PSM, there were 134 (11.8%) patients reached the combined endpoints, which included 77 in 566 patients (14.6%) in low bilirubin group and 57 in 566 patients (10.1%) in high bilirubin group (p=0.039). The results of three models (including demographics, pathological, clinical indicators and serum bilirubin) demonstrated that a lower basic serum bilirubin level was significantly associated with a higher risk of reaching combined endpoints in IgAN patients both in unmatched and matched cohort. Conclusion: Serum bilirubin level may be negatively associated with the progression of IgAN.

Total bilirubin is negatively related to diabetes mellitus in Chinese elderly: a community study

Background

Serum total bilirubin (TB) was used as a predictor of diabetes mellitus (DM) and this study was undertaken to investigate the relationship between serum TB and DM.

Methods

In this cross-sectional study, a total of 3,867 subjects older than 65 years were recruited from East China. The anthropometric data, lifestyle and past history were collected. The fasting blood glucose, total cholesterol (TC), triglycerides (TGs), TB and alanine aminotransferase (ALT) were detected. The prevalence of DM was calculated for every serum TB quartile. Logistic regression analysis was employed to evaluate the relationship between serum TB and DM.

Results

Serum TB was significantly higher in non-DM than DM patients (P=0.001). Serum TB was negatively related to the prevalence of DM (P=0.004). Logistic regression analysis revealed that serum TB was an independent prognostic factor of DM [odds ratio (OR): 0.876, 95% confidence interval (CI): 0.807-0.951].

Conclusions

Our results showed serum TB in physiological range is an independent risk factor of DM in old people; the prevalence of DM in old people has a linear relationship with serum TB quartiles; the prevalence of DM reduces with the increasing of serum TB within physiological range.

Association of Lower Serum Bilirubin With Loss of Residual Kidney Function in Peritoneal Dialysis Patients

Bilirubin is recognized as an endogenous antioxidant, and low serum bilirubin is reported to be associated with the progression of kidney disease. However, it is unclear whether serum bilirubin levels are associated with the loss of residual kidney function (RKF) in peritoneal dialysis (PD) patients. This study investigated the relationship between serum total bilirubin and loss of RKF. We prospectively followed 94 PD patients who started PD in our hospital between June 2006 and May 2016. Ten patients who had chronic liver disease or cirrhosis were excluded. Patients were divided into three groups based on serum total bilirubin concentration tertiles: tertile 1 (T1) < 0.3, T2 = 0.3, and T3 ≥ 0.4 mg/dL. We estimated the relationship between serum bilirubin and loss of RKF, defined as daily urine volume (<100 mL) within 3 years after starting PD, using a Cox proportional hazards model. During the 3-year observation period, 22 patients lost RKF. The incidence rate of loss of RKF increased linearly with the decrease in serum total bilirubin levels (P for trend < 0.05). After adjusting for confounding factors, low serum total bilirubin level was shown to be an independent predictor of loss of RKF (hazard ratio [HR] for every 0.1 mg/dL decrease, 1.50; 95% confidence interval [CI], 1.01-2.51; HR [95%CI] for T2 and T1 [vs. T3] 2.03 [0.65-7.88] and 3.70 [1.00-15.9]). This study suggests that low serum total bilirubin levels are associated with the loss of RKF in PD patients.

THE ASSOCIATION OF SERUM BILIRUBIN ON KIDNEY CLINICOPATHOLOGIC FEATURES AND RENAL OUTCOME IN PATIENTS WITH DIABETIC NEPHROPATHY: A BIOPSY-BASED STUDY

Objective: To explore the relationship between serum bilirubin concentration and clinicopathologic features and renal outcome in biopsy-diagnosed diabetic nephropathy (DN) in patients with type 2 diabetes mellitus. Methods: In this retrospective study, 118 patients with DN were enrolled. Participants were divided into two groups according to their median baseline serum bilirubin concentration: Group 1 (serum bilirubin ≤7.5 μmol /L); Group 2 (serum bilirubin >7.5 μmol /L). Basic clinical parameters were measured at the time of renal biopsy, and the relationships between serum bilirubin and the clinicopathologic features and renal outcome were analyzed. Results: Patients in Group 1 often had inferior renal function. Compared with Group 2, the glomerular classification and interstitial inflammation were more severe in subjects of Group 1, while arteriolar hyalinosis and interstitial fibrosis and tubular atrophy (IFTA) were comparable between the groups. Serum bilirubin was negatively correlated with the severity of the glomerular classification, interstitial inflammation, and IFTA. In the prognostic analysis, higher serum bilirubin level was associated with a lower risk of progression to end-stage renal disease, which was independent of the effects of age, gender, duration of diabetes, anemia, serum glucose, and hypertension but not of estimated glomerular filtration rate (hazard ratio, 0.406; 95% confidence interval, 0.074 to 2.225; P = .299). Conclusion: Our study showed a negative correlation between serum bilirubin level and renal pathologic lesions in patients with DN; serum bilirubin showed an inverse association with DN progression, but this was not independent. Abbreviations: CI = confidence interval; CKD = chronic kidney disease; DM = diabetes mellitus; DN = diabetic nephropathy; DR = diabetic retinopathy; eGFR = estimated glomerular filtration rate; ESRD = end-stage renal disease; HbA1c = glycated hemoglobin; HO-1 = heme oxygenase 1; HR = hazard ratio; IFTA = interstitial fibrosis and tubular atrophy; log-BIL = log-transformed baseline serum bilirubin; T2DM = type 2 diabetes mellitus.

Association of serum bilirubin with renal outcomes in Han Chinese patients with chronic kidney disease

BACKGROUND

Oxidative stress and inflammation play pivotal roles in chronic kidney disease (CKD). Bilirubin is an endogenous anti-inflammatory antioxidant. However, the relationship between serum bilirubin and renal outcomes in CKD is controversial. We explored the association of serum bilirubin levels with renal outcomes in Han Chinese patients with CKD.

METHODS

Clinical and laboratory data were collected from 316 patients with CKD. The primary clinical endpoint was renal replacement therapy or death. The association between serum bilirubin and clinical parameters was assessed by correlation analysis. Multiple Cox regression analysis was used to explore the relationship between serum bilirubin and renal outcomes in patients with CKD.

RESULTS

Serum total and indirect bilirubin were positively correlated with estimated glomerular filtration rate, but negatively correlated with 24-h urine protein in patients with CKD. Serum total and indirect bilirubin were inversely associated with CKD stages in patients with CKD stages 1-5. Multiple Cox regression analysis demonstrated that the higher concentration of serum total bilirubin was independently associated with better renal outcomes in CKD.

CONCLUSIONS

Our results suggest that serum total bilirubin may have protective effects on kidneys.

Hyperbilirubinemia, Hypertension, and CKD: the Links

PURPOSE OF REVIEW

This review aims to highlight recent advances on the role of hyperbilirubinemia in hypertension and chronic kidney disease, with a focus on the pathophysiological mechanisms explaining the protective effects of bilirubin. An overview of pharmacologic induction of hyperbilirubinemia will also be discussed.

RECENT FINDINGS

The findings depict a protective role of bilirubin in the development of hypertension and cardiovascular diseases. Hyperbilirubinemia is also negatively correlated with the development and progression of chronic kidney disease. Commonly used drugs play a role in pharmacologic induction of hyperbilirubinemia. Bilirubin is therefore an exciting target for new therapeutic interventions for its antioxidant properties can be pivotal in the management of hypertension and in preventing and halting the progression of chronic kidney disease. Longitudinal studies are warranted to evaluate the prospective association between bilirubin levels and incident hypertension and chronic kidney disease in the general population. Interventions to induce hyperbilirubinemia need to be explored as a novel therapeutic approach in fighting disease burden.

Independent and combined effect of bilirubin and smoking on the progression of chronic kidney disease

Objective

Whether serum bilirubin and cigarette smoking affect the risk of renal function decline remains inconclusive. We aimed to test the independent and combined effects of bilirubin and cigarette smoking on the progression of chronic kidney disease (CKD) in hypertensive adults.

Methods

The study population consisted of 12,633 patients in the renal sub-study of the China Stroke Primary Prevention Trial. The primary outcome was progression of CKD, defined as a decrease in estimated glomerular filtration rate (eGFR) of ≥30% and to a level of <60 mL/min/1.73 m² if baseline eGFR was ≥60 mL/min/1.73 m², or a decrease in eGFR of ≥50% if baseline eGFR was <60 mL/min/1.73 m², or end-stage renal disease. The secondary outcomes included 1) rapid decline in renal function and 2) annual rate of eGFR decline.

Results

The median follow-up duration was 4.4 years. Cigarette smoking had no significant effect on the progression of CKD (odds ratio [OR]: 1.11, 95% confidence interval [95% CI]: 0.78-1.57). However, a significantly lower risk of the primary event (OR: 0.72, 95% CI: 0.55-0.95) was found in participants in tertile 3 compared to those in tertiles 1-2 for total bilirubin (TBiL) levels. More importantly, there was an interaction between TBiL and smoking status on the primary outcome (P for interaction =0.013). Among ever smokers, TBiL levels had no significant effect on the primary outcome. However, among never smokers, higher TBiL levels were significantly associated with a lower risk of the primary outcome (tertile 3 vs 1-2; OR: 0.53, 95% CI: 0.36-0.78). Similar trends were observed for direct bilirubin and secondary outcomes.

Conclusion

Among hypertensive patients, bilirubin was inversely associated with the progression of CKD in never smokers, but not in ever smokers.

The Association between Serum Bilirubin Level and Electrochemical Skin Conductance in Chinese Patients with Type 2 Diabetes

Bilirubin is an antioxidant and plays a protective role against cardiovascular and microvascular disease. The aim of this study is to explore the possible protective effect of bilirubin on small nerve function. A total of 265 Chinese patients with type 2 diabetes mellitus (T2DM) were enrolled in the study. Both SUDOSCAN and other traditional diabetic neuropathy examinations including neuropathy symptom score (NSS), the neuropathy disability score (NDS) and Michigan Neuropathy Screening Instrument (MNSI) scores were performed in all patients with T2DM. Blood bilirubin levels were tested in the study. Spearman correlation analysis and multivariate regression analysis were performed to determine the relation between bilirubin level and hands and feet ESC values. Spearman correlation analysis demonstrated a correlation between total bilirubin and ESC levels including hands (r = 0.165, P < 0.05) and feet (r = 0.122, P < 0.05) as well as between UCBil and ESC levels including both hands (r = 0.172, P < 0.05) and feet (r = 0.175, P < 0.05). Multivariate regression linear analyses showed both total bilirubin and UCBil level were independently associated with hands and feet ESC levels. All these results suggested a positive association between bilirubin level and ESC level, indicating a possible protective role of bilirubin in peripheral small nerve dysfunction of type 2 diabetes mellitus.

Relationship between serum total bilirubin levels and mortality in uremia patients undergoing long-term hemodialysis: A nationwide cohort study

BACKGROUND AND AIMS

Previous studies show that serum bilirubin has potent antioxidant effect and is associated with protection from kidney damage and reduce cardiovascular events. The aim of this study was to examine the association of serum total bilirubin level and mortality in uremia patients who underwent hemodialysis.

METHODS

This is a nationwide retrospective long-term cohort study. Patients were registered in the Taiwan Renal Registry Data System (TWRDS) from 2005 to 2012. A total of 115,535 hemodialysis patients were surveyed and those with valid baseline total bilirubin (TB) data were enrolled. All-cause mortality was the primary outcome.

RESULTS

A total of 47,650 hemodialysis patients followed for 27.6 ± 12 months, were divided into 3 groups according to different baseline serum total bilirubin levels (0.1-0.3, 0.3-0.7, 0.7-1.2 mg/dL). Mean age was 61.4 ± 13.6 years, 50% were male, 13% were hepatitis B carriers, and 20% were hepatitis C carriers. Primary outcome was the 3-year mortality. The TB level 0.7-1.2 mg/dL group had high mortality, statistically significant hazard ratio of mortality was 1.14 (crude HR, 95% 1.07-1.20, p < 0.01), and adjusted HR was 1.18 (model 1, 95% CI 1.11-1.25), 1.21 (model 2, 95% CI 1.14-1.29, p < 0.01), 1.44 (model 3, 95% CI 1.06-1.96, p < 0.01), respectively. Sensitivity test showed that after excluding 14,899 patients with hepatitis B or C, or abnormal liver function, the highest level of TB associated with higher significant mortality was still robust.

CONCLUSIONS

In our study, high TB level is associated with mortality in uremia patients undergoing long-term hemodialysis, but further studies of the different effects of unconjugated or conjugated bilirubin on hemodialysis patients are needed.

Low serum bilirubin level predicts the development of chronic kidney disease in patients with type 2 diabetes mellitus

BACKGROUND/AIMS

We evaluated whether serum bilirubin levels can predict the development of chronic kidney disease (CKD) in patients with type 2 diabetes mellitus (T2DM).

METHODS

This was a retrospective observational longitudinal study of patients presenting at the Pusan National University Hospital. A total of 349 patients with T2DM and preserved kidney function (estimated glomerular filtration rate ≥ 60 mL/min/1.73 m²) were enrolled. The main outcome was the development of CKD stage 3 or greater. The patients were divided into four groups according to the quartiles of the total serum bilirubin levels at baseline.

RESULTS

The group with the lowest range of total serum bilirubin level (Q1) showed the highest cumulative incidence of CKD stage 3 or greater than that of the other lower quartiles (Q1 vs. Q4; hazard ratio [HR], 6.75; 95% confidence interval [CI], 1.54 to 29.47; p = 0.011). In multivariate analysis, the risk of developing CKD stage 3 or greater was higher in the second lowest quartile of the serum bilirubin level than that in the highest quartile of the serum bilirubin level (Q2 vs. Q4; HR, 9.36; 95% CI, 1.33 to 65.73; p = 0.024). In the normoalbuminuria subgroup (n = 236), multivariate analysis showed that the risk of developing CKD stage 3 or greater was higher in the lowest quartile of the serum bilirubin level than that in the highest quartile of the serum bilirubin level (Q1 vs. Q4; HR, 7.36; 95% CI, 1.24 to 35.82; p = 0.019).

CONCLUSIONS

Serum bilirubin might be an early clinical marker for predicting the progression of CKD in patients with T2DM and preserved renal function.

Bilirubin concentration is positively associated with haemoglobin concentration and inversely associated with albumin to creatinine ratio among Indigenous Australians: eGFR Study

Low serum bilirubin concentrations are reported to be strongly associated with cardio-metabolic disease, but this relationship has not been reported among Indigenous Australian people who are known to be at high risk for diabetes and chronic kidney disease (CKD).

HYPOTHESIS

serum bilirubin will be negatively associated with markers of chronic disease, including CKD and anaemia among Indigenous Australians.

METHOD

A cross-sectional analysis of 594 adult Aboriginal and Torres Strait Islander (TSI) people in good health or with diabetes and markers of CKD. Measures included urine albumin: creatinine ratio (ACR), estimated glomerular filtration rate (eGFR), haemoglobin (Hb) and glycated haemoglobin (HbA1c). Diabetes was defined by medical history, medications or HbA1c≥6.5% or ≥48mmol/mol. Anaemia was defined as Hb<130g/L or <120g/L in males and females respectively. A multivariate regression analysis examining factors independently associated with log-bilirubin was performed.

RESULTS

Participants mean (SD) age was 45.1 (14.5) years, and included 62.5% females, 71.7% Aboriginal, 41.1% with diabetes, 16.7% with anaemia, 41% with ACR>3mg/mmol and 18.2% with eGFR<60mL/min/1.73m². Median bilirubin concentration was lower in females than males (6 v 8μmol/L, p<0.001) and in Aboriginal than TSI participants (6 v 9.5μmol/L, p<0.001). Six factors explained 35% of the variance of log-bilirubin; Hb and cholesterol (both positively related) and ACR, triglycerides, Aboriginal ethnicity and female gender (all inversely related).

CONCLUSION

Serum bilirubin concentrations were positively associated with Hb and total cholesterol, and inversely associated with ACR. Further research to determine reasons explaining lower bilirubin concentrations among Aboriginal compared with TSI participants are needed.

Serum bilirubin levels are negatively associated with diabetic retinopathy in patients with type 1 diabetes and normal renal function

INTRODUCTION

Previous studies suggested that total serum bilirubin levels are negatively associated with diabetic retinopathy (DR) and nephropathy in patients with diabetes mellitus. The objective of this study was to explore the relationship between serum total bilirubin levels and prevalence of DR in patients with type 1 diabetes (T1DM) and normal renal function.

METHODS

Study included 163 T1DM with normal renal function (urinary albumin excretion rate <30 mg/24 h, estimated glomerular filtration rate (eGFR) >60 ml min^-11.73 m^-2). Photo-documented retinopathy status was made according to the EURODIAB protocol.

RESULTS

Patients with DR were older (49 vs 42 years, p = 0.001), had higher systolic blood pressure (130 vs 120 mmHg, p = 0.001), triglycerides (0.89 vs 0.77 mmol/L, p = 0.01), and lower serum total bilirubin (12 vs 15 U/L, p = 0.02) and eGFR (100 vs 106 ml min^-11.73 m^-2, p = 0.03). In multivariate logistic regression analysis, only total serum bilirubin was significantly associated with risk of DR in our subjects (OR 0.88, CI 0.81-0.96, p = 0.006).

CONCLUSION

These data suggest that serum total bilirubin levels are independently negatively associated with DR in T1DM with normal renal function. Prospective studies are needed to confirm whether lower serum total bilirubin has predictive value for the development of DR in T1DM with normal renal function.

Anemia, bilirubin, and cardiovascular autonomic neuropathy in patients with type 2 diabetes

To investigate the relationship among anemia, physiological serum bilirubin levels, and cardiovascular autonomic neuropathy (CAN) in subjects with type 2 diabetes. In total, 2230 subjects with type 2 diabetes were evaluated in this cross-sectional study. CAN was diagnosed with a cardiovascular reflex test. The prevalence of anemia was greater in subjects with CAN. In multivariable analysis, the relationship between anemia and CAN remained statistically significant after adjusting for the risk factors (odds ratio [OR] 1.39; 95% confidence interval [CI] 1.07-1.80, P = .015). Additional adjustment for serum bilirubin concentrations abolished this relationship (OR 1.20, 95% CI 0.91-1.58, P = .189). Anemia is positively associated with the prevalence of CAN in subjects with type 2 diabetes. In addition, our results suggest that the putative increased CAN risk associated with anemia might be mediated by a correlated decrease in serum bilirubin levels.

Identification of potential antioxidant indices by biogenic gold nanoparticles in hyperglycemic Wistar rats

Oxidative stress is a crucial factor in diabetes, where the abnormal metabolic ambience leads to hyperglycemia resulting in the onset of several vascular complications. Under homeostasis, innate antioxidants efficiently inhibit the oxidative stress, thereby restrain further progression of diabetes. In the present study, a potential antioxidant marker was identified from hepatic tissue of diabetic Wistar rats after oral administration of biogenic gold nanoparticles (GNPs). Diabetic animals treated with GNPs showed increase in insulin level and subsequently reduced the concentration of blood glucose level to normal. Further, GNPs favoured to retain the hepatic enzymatic markers, serum lipid levels and followed by renal biochemical profile in the rats. In addition, GNPs treated rats displayed an elevated level of lipid peroxidation, superoxide dismutase, glutathione peroxidase, and catalase enzymatic activity. Consequently, GNPs treated rats showed diminished level of histological injury in the hepatic, renal, and pancreatic tissues. Taken together, these results suggested that among the several antioxidant enzymes, catalase elucidated the highest area under curve (AUC) with 0.80 accomplished by receiver operating characteristic (ROC) curve. Collectively, our findings enlighten that GNPs treated rat able to alleviate the hyperglycemic condition due to the enzymatic activity of catalase.

Serum bilirubin concentrations and incident coronary heart disease risk among patients with type 2 diabetes: the Dongfeng-Tongji cohort

AIMS

Elevated serum bilirubin levels are associated with decreased coronary heart disease (CHD) risk in cross-sectional studies among diabetic patients, but prospective evidence is limited. We investigated the relationship of serum bilirubin levels with incident CHD risk among type 2 diabetes patients.

METHODS

In a prospective study of 2918 type 2 diabetes embedded in the Dongfeng-Tongji cohort, serum total bilirubin (TBil), direct bilirubin (DBil), and indirect bilirubin (IBil) were measured at baseline. Cox proportional hazards models were used to examine the association between serum bilirubin levels and CHD risk.

RESULTS

A total of 440 CHD cases were identified during 12,017 person-years of follow-up. Compared with extreme quartiles, the adjusted hazard ratio and 95% confidence interval of incident CHD were 0.74 (0.56-0.99) with P trend = 0.08 in IBil, while in TBil and DBil, the bilirubin-CHD associations were not significant. Moreover, serum TBil and IBil levels were interacted with drinking status on the risk of incident CHD (P interaction = 0.021 and 0.037, respectively), and the associations were evident in ever drinkers. In drinkers, when serum TBil or IBil concentrations increased 1 μmol/L, the CHD risk both decreased 6% (95% CIs 0.89-0.99 and 0.87-1.00, respectively).

CONCLUSIONS

Serum IBil levels were marginally related to decreased incident CHD risk among type 2 diabetes. Drinking could potentially enhance the associations of serum TBil and DBil levels with incident CHD risk.

Total bilirubin level may be a biomarker of nephropathy in type 2 diabetes mellitus: A meta-analysis of observational studies based on MOOSE compliant

Recently, the number of the studies on the relationship between the total bilirubin level (TBL) and diabetic nephropathy (DN) is increasing, but their results were not consistent. Therefore, we performed a meta-analysis to analyze the relationship between TBL and the risk of DN.We searched 5 databases before October 31, 2016, and reviewed the reference list of relevant articles. The fixed or random-effects model was used to pool risk estimates. We conducted the dose-response meta-analysis to evaluate the relationship between TBL and the risk of DN.Our meta-analysis showed that TBL in the DN group was lower than that in diabetes without the kidney disease (NDN) group (standard mean difference [SMD]: -0.63, 95% CI: -0.80, -0.46). The result of each subgroup also showed that TBL in the DN group was lower than that in the NDN group. The result of meta-regression indicated that duration of diabetes mellitus might be the source of heterogeneity. Our meta-analysis also showed that there was a significant negative relationship between TBL and the risk of DN (OR: 0.86, 95%CI: 0.82, 0.90). The results of subgroup analysis were similar to those of SMD; no sources of heterogeneity were detected by meta-regression. Sensitivity analysis indicated that the results were robust. We observed a linear association between TBL and the risk of DN, and there was a negative dose-response association between TBL and the risk of DN.In conclusion, bilirubin may be used as a biomarker of DN. It helps early diagnosis and effective therapeutic strategies on DN.

Relationship between kidney function decline and initial risk factors for the progression of diabetic kidney disease: a retrospective analysis of 91 Japanese patients with type 2 diabetes

BACKGROUND

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease (ESRD) in Japan. The clinical course and factors related to the progression of DKD to ESRD are important issues when treating patients with DKD.

METHODS

Ninety-one type 2 diabetic patients with DKD that had progressed from chronic kidney disease (CKD) stages G1-3 on their initial clinical visit to ESRD were enrolled. The decline in the estimated glomerular filtration rate (eGFR) was analyzed and the initial clinical factors that influenced the decline rate were explored.

RESULTS

There was a linear decline in eGFR before progression to ESRD, with a median annual decline rate (∆eGFR) of 9.2 mL/min/1.73 m2. In all patients, a history of coronary artery disease and increased levels of initial eGFR and high-density lipoprotein cholesterol (HDL-C) were positive predictors of log ∆eGFR, whereas age, history of cerebral infarction (CI), and an increased level of serum albumin were negative predictors of log ∆eGFR. In patients with CKD stages G1-2 on their first visit, male sex and increased diastolic blood pressure were positive predictors. In patients with CKD stage G3 on their first visit, an increased level of LDL-C was a positive predictor, whereas a history of CI and an increased level of serum total bilirubin (TBil) were negative predictors.

CONCLUSION

In addition to the common risk factors, initial eGFR, HDL-C, and TBil were identified as novel risk factors for ESRD. These risk factors may differ between patients with early and advanced stages of CKD.

Association between serum bilirubin levels and decline in estimated glomerular filtration rate among patients with type 2 diabetes

AIMS

Studies indicate that elevated serum total bilirubin (TBil) levels are associated with lower risk of diabetic kidney disease (DKD). Few studies examined the associations of direct bilirubin (DBil) and indirect bilirubin (IBil) with the development of DKD.

METHODS

Type 2 diabetes patients (n=2,958) with estimated glomerular filtration (eGFR)≥60mlmin(-1) 1.73m(-2) from the Dongfeng-Tongji cohort were selected and followed up for 5years. Development of DKD was defined as decline in eGFR≥30% during follow-up. Generalize linear model was used to assess the associations of bilirubin levels with DKD development.

RESULTS

Compared with those in the first tertile of serum TBil, the relative risks (RRs) and 95% confidence intervals (CIs) of incident eGFR decline for tertile 2 to 3 were 0.83 (0.64-1.09) and 0.74 (0.56-0.98), Ptrend=0.04. The counterpart RRs (95% CIs) in IBil were 0.74 (0.57-0.97) and 0.75 (0.57-0.98), Ptrend=0.04. No significant associations were observed in DBil. Moreover, TBil and IBil interacted with smoking, the bilirubin-DKD associations were evident in ever smokers.

CONCLUSIONS

Our findings suggest that elevation of serum TBil or IBil levels are independent protective factors for development of DKD, particularly in smokers.

Association of circulating total bilirubin with the metabolic syndrome and type 2 diabetes: A systematic review and meta-analysis of observational evidence

OBJECTIVE

Emerging evidence suggests that bilirubin levels might be associated with the metabolic syndrome (MetS) and type 2 diabetes (T2D), although the nature of the association remains unclear.

DESIGN

This systematic review and meta-analysis investigated the relationship between total plasma bilirubin and the risk of MetS and T2D.

DATA SOURCES

Relevant studies were identified using five databases (Embase, Medline [Ovid], Web of Science, PubMed, Cochrane Central and Google Scholar), with the last search done on 21 October 2015. Study references were checked and authors contacted to identify additional studies.

STUDY SELECTION

Randomized controlled trials, and cohort, case-control and cross-sectional studies of adults examining the association between blood bilirubin levels and MetS and T2D were included, irrespective of language and date of publication. Abstract and full-text selection was done by two independent reviewers, with a third reviewer available in case of disagreement.

DATA EXTRACTION

Data were extracted by two independent reviewers using a predesigned data collection form.

MAIN OUTCOMES AND MEASURES

MetS and T2D.

METHODS

Summary estimates were obtained by random-effects meta-analysis.

RESULTS

Of the 2313 searched references, 16 observational studies (11 cross-sectional, two prospective, one that was both cross-sectional and prospective, two retrospective and one national survey) met our inclusion criteria. Overall, data were available for 175,911 non-overlapping participants, including 7414 MetS cases and 9406 T2D cases. In the meta-analysis of seven cross-sectional studies, the pooled odds ratio (95% confidence interval) for MetS in a comparison of extreme tertiles of serum bilirubin levels was 0.70 (95% CI: 0.62, 0.78), whereas no significant association was found for the pooled estimated relative risk between two prospective studies (0.57, 95% CI: 0.11, 2.94). The corresponding estimate was 0.77 (95% CI: 0.67, 0.87) for T2D from four cross-sectional studies.

CONCLUSION

The available evidence, mainly from cross-sectional studies, supports an inverse association of bilirubin levels with adverse metabolic outcomes. Large-scale prospective studies are now needed to establish whether bilirubin levels may be useful in the prevention of MetS and T2D.

Does bilirubin protect against developing diabetes mellitus?

After 25 years of evaluating bilirubin as a possible protective agent in neonatal and cardiovascular disease, interest has moved on to a exploring a possible protective role in diabetes mellitus (DM). This review finds conflicting prospective data for a protective relationship though there are retrospective, case-controlled data, that can only show association, which is not causality. Only prospective studies can show causality. Also, it would appear that the underlying biochemical assumptions do not readily translate from the animal to the human setting. Given that many factors impact on circulating bilirubin levels, it is not surprising that a clear-cut answer is not available; the jury is still out. Any relationship between DM and bilirubin might relate to intermediates in bilirubin metabolism, including relationships involving the genes for the enzymes participating in those steps. Nevertheless, the pursuit of bilirubin in disease causation is opening new avenues for research and if it is established that serum bilirubin can predict risks, much will have been achieved. The answer may have to come from molecular genetic analyses.

Serum Bilirubin and Their Association With C-Reactive Protein in Patients With Migraine

BACKGROUND

Increased levels of C-reactive protein (CRP) have been considered as a marker in assessing neurogenic inflammation of migraine patients. An inverse relationship between serum bilirubin and CRP has been observed in various diseases. Therefore, we analyzed serum bilirubin levels in migraine patients, and investigated the relationship between serum bilirubin and CRP in migraineurs.

METHODS

A total of 86 newly diagnosed migraine patients were consecutively recruited to this study.

RESULTS

Significantly lower median serum total bilirubin, conjugated bilirubin (CB) and unconjugated bilirubin were found in patients with migraine than healthy controls, and the levels of CRP were significantly higher in migraine patients than healthy controls. A negative correlation between CRP and CB was observed in patients with migraine (r = -0.255, P = 0.018). In a multiple linear regression model, the concentrations of CRP remained negatively correlated with CB.

CONCLUSIONS

Our study demonstrates that serum bilirubin concentrations are decreased in migraineurs, and CB levels were found to be positively correlated with CRP in migraine patents. However, larger cross-sectional and prospective studies are needed to establish whether serum bilirubin may be a useful biomarker for assessing neurogenic inflammation in migraine patients and eventually guiding the therapy.

Innovative biomarkers for predicting type 2 diabetes mellitus: relevance to dietary management of frailty in older adults

Type 2 diabetes mellitus (T2DM) increases in prevalence in the elderly. There is evidence for significant muscle loss and accelerated cognitive impairment in older adults with T2DM; these comorbidities are critical features of frailty. In the early stages of T2DM, insulin sensitivity can be improved by a "healthy" diet. Management of insulin resistance by diet in people over 65 years of age should be carefully re-evaluated because of the risk for falling due to hypoglycaemia. To date, an optimal dietary programme for older adults with insulin resistance and T2DM has not been described. The use of biomarkers to identify those at risk for T2DM will enable clinicians to offer early dietary advice that will delay onset of disease and of frailty. Here we have used an in silico literature search for putative novel biomarkers of T2DM risk and frailty. We suggest that plasma bilirubin, plasma, urinary DPP4-positive microparticles and plasma pigment epithelium-derived factor merit further investigation as predictive biomarkers for T2DM and frailty risk in older adults. Bilirubin is screened routinely in clinical practice. Measurement of specific microparticle frequency in urine is less invasive than a blood sample so is a good choice for biomonitoring. Future studies should investigate whether early dietary changes, such as increased intake of whey protein and micronutrients that improve muscle function and insulin sensitivity, affect biomarkers and can reduce the longer term complication of frailty in people at risk for T2DM.

Inverse association between serum total bilirubin levels and diabetic peripheral neuropathy in patients with type 2 diabetes

Several studies have suggested that bilirubin, a potent innate antioxidant, plays a protective role against cardiovascular and microvascular disease. This study investigated the association between serum concentrations of total bilirubin (TB) and the presence of diabetic peripheral neuropathy (DPN) in Korean diabetic patients. This cross-sectional study involved 1207 patients aged more than 30 years with type 2 diabetes. DPN was assessed according to clinical symptoms and physical examinations using Michigan Neuropathy Screening Instrument examination score, 10-g monofilament sensation, and current perception threshold. The subjects were stratified into gender-specific tertiles based on TB values, and the relationship between the TB values and DPN was analyzed. Compared with patients within the lowest TB tertile, those with higher TB levels consisted of patients with shorter duration of diabetes, lower HbA1c, better renal function, and less autonomic neuropathy, retinopathy, and albuminuria. Serum TB levels were inversely associated with DPN. In multivariate analysis for the development of DPN after adjusting for potential confounding factors including retinopathy, albuminuria, and autonomic neuropathy, the TB levels were inversely associated with the presence of DPN, both as a continuous variable [odds ratio (OR) per log standard deviation (SD) 0.79; 95% confidence interval (CI) 0.65-0.97; P = 0.022] and when categorized in tertiles (the highest vs. the lowest tertile; OR 0.63; 95% CI 0.40-0.99; P = 0.046). Low serum bilirubin levels are significantly associated with DPN, independently of classic risk factors and other microvascular complications. Further investigation is necessary to determine whether serum bilirubin has a prognostic significance on DPN.

Serum bilirubin concentration is associated with eGFR and urinary albumin excretion in patients with type 1 diabetes mellitus

AIMS

Although relationships of serum bilirubin concentration with estimated glomerular filtration rate (eGFR) and urinary albumin excretion (UAE) in patients with type 2 diabetes have been reported, whether such relationships exist in patients with type 1 diabetes is unknown.

METHODS

A total of 123 patients with type 1 diabetes were investigated in this cross-sectional study. The relationship between bilirubin (total and indirect) concentrations and log(UAE) as well as eGFR was examined by Pearson's correlation analyses. Multivariate regression analyses were used to assess the association of bilirubin (total and indirect) with eGFR as well as log(UAE).

RESULTS

A positive correlation was found between serum bilirubin concentration and eGFR; total bilirubin (r=0.223, p=0.013), indirect bilirubin (r=0.244, p=0.007). A negative correlation was found between serum bilirubin concentration and log(UAE); total bilirubin (r=-0.258, p=0.005), indirect bilirubin (r=-0.271, p=0.003). Multivariate regression analyses showed that indirect bilirubin concentration was an independent determinant of eGFR and log(UAE).

CONCLUSIONS

Bilirubin concentration is associated with both eGFR and log(UAE) in patients with type 1 diabetes. Bilirubin might have a protective role in the progression of type 1 diabetic nephropathy.

Serum Total Bilirubin Levels Provide Additive Risk Information over the Framingham Risk Score for Identifying Asymptomatic Diabetic Patients at Higher Risk for Coronary Artery Stenosis

BACKGROUND

The diagnosis of coronary artery disease (CAD) is often delayed in patients with type 2 diabetes. Serum total bilirubin levels are inversely associated with CAD. However, no studies have examined whether this can be used as a biochemical marker for identifying asymptomatic diabetic patients at higher risk for having obstructive CAD.

METHODS

We performed a cross-sectional study of 460 consecutive asymptomatic patients with type 2 diabetes. All patients underwent coronary computed tomographic angiography, and their serum total bilirubin levels were measured. Obstructive CAD was defined as ≥50% diameter stenosis in at least one coronary artery.

RESULTS

Serum total bilirubin tertiles showed an inverse association with the prevalence of obstructive CAD. In multivariate logistic regression analysis, the odds ratio for the highest versus the lowest tertile of total bilirubin was 0.227 (95% confidence interval [CI], 0.130 to 0.398), and an increment of 1 µmol/L in serum total bilirubin level was associated with a 14.6% decrease in obstructive CAD after adjustment for confounding variables. Receiver operating characteristic curve analysis showed that the area under the curve for the Framingham Risk Score (FRS) plus serum total bilirubin level was 0.712 (95% CI, 0.668 to 0.753), which is significantly greater than that of the FRS alone (P=0.0028).

CONCLUSION

Serum total bilirubin level is inversely associated with obstructive CAD and provides additive risk information over the FRS. Serum total bilirubin may be helpful for identifying asymptomatic patients with type 2 diabetes who are at higher risk for obstructive CAD.

Mildly elevated serum total bilirubin levels are negatively associated with carotid atherosclerosis among elderly persons with type 2 diabetes

Diabetes is strongly associated with several mechanisms of tissue damage such as oxidative stress. Serum bilirubin may have a beneficial role in preventing oxidative changes in cardiovascular disease (CVD). Limited information is available on whether serum bilirubin is an independent confounding factor for carotid atherosclerosis among elderly persons with type 2 diabetes. The study subjects were 169 men aged 79 ± 8 (mean ± SD) years and 205 women aged 81 ± 8 years that were enrolled consecutively from patients in the medical department. Carotid intima-media thickness (IMT) and plaque were derived via B-mode ultrasonography. Multiple linear regression analysis showed that serum total bilirubin (β = -0.160) was significantly associated with carotid IMT. Compared to subjects with a serum total bilirubin of tertile-1 (0.13-0.58 mg/dL), the multivariate-adjusted odds ratio (95% confidence interval) of carotid IMT ≥1.0 mm including plaque and carotid plaque was 0.46 (0.23-0.93) and 0.32 (0.17-0.60) in the Tertile-3 group (0.87-1.93 mg/dL), respectively. Next, data were further stratified by gender, age, smoking status, medication and prevalence of CVD. There were no significant differences in serum total bilirubin levels between selected subgroups. Our data demonstrated a negative association between serum total bilirubin and carotid atherosclerosis among elderly persons with type 2 diabetes.

Association of serum total bilirubin with renal outcome in Japanese patients with stages 3-5 chronic kidney disease

OBJECTIVE

Serum bilirubin has been reported to be associated with the progression of kidney disease in patients with diabetic nephropathy. Less is known, however, about the relationship between bilirubin and chronic kidney disease (CKD) of other etiologies. This study was designed to clarify whether serum total bilirubin concentration is associated with kidney disease progression in patients with CKD independent of etiology.

MATERIALS AND METHODS

This prospective observational study enrolled 279 consecutive patients with stages 3-5 CKD. The renal endpoint was the composite of the doubling of serum creatinine or end-stage renal disease requiring dialysis. Patients were divided into three groups by their serum total bilirubin concentrations: ≤0.3 (lowest), 0.4-0.5 (middle), and ≥0.6 (highest) mg/dL. A Cox proportional hazards model was applied to determine the risk factors for poor renal outcome.

RESULTS

The median follow-up period was 21months. One-hundred and three patients reached renal end points. After multivariable adjustment, a 0.1mg/dL increase in serum bilirubin was associated negatively with poor renal outcome (hazard ratio [HR], 0.73; 95% confidence interval [CI], 0.60-0.87). In addition, after adjustment for confounding factors, including traditional and nontraditional cardiovascular risk factors, the middle (HR 3.14, 95% CI 1.36-8.57) and lowest (HR 4.22, 95% CI 1.81-11.59) bilirubin groups had significantly higher HRs for renal outcome than the highest bilirubin group.

CONCLUSIONS

Lower serum bilirubin concentration was independently associated with adverse renal outcomes, suggesting that the measurement of serum bilirubin is useful for predicting kidney disease progression in patients with moderate to severe CKD.

Bilirubin exerts pro-angiogenic property through Akt-eNOS-dependent pathway

Low serum bilirubin levels are associated with the risk of cardiovascular diseases including peripheral artery disease. Bilirubin is known to exert its property such as antioxidant effect or the enhancement of flow-mediated vasodilation, however, bilirubin action on angiogenesis remains unclear. To investigate the molecular mechanism of bilirubin on angiogenic effect, we first employed C57BL/6J mice with unilateral hindlimb ischemia surgery and divided the mice into two groups (vehicle-treated group and bilirubin-treated group). The analysis of laser speckle blood flow demonstrated the enhancement of blood flow recovery in response to ischemia of mice with bilirubin treatment. The density of capillaries was significantly higher in ischemic-adductor muscles of bilirubin-treated mice. The phosphorylated levels of endothelial nitric oxide synthase (eNOS) and Akt were increased in ischemic skeletal muscles of mice with bilirubin treatment compared with vehicle treatment. In in vitro experiments by using human aortic endothelial cells, bilirubin augmented eNOS and Akt phosphorylation, cell proliferation, cell migration and tube formation. These bilirubin actions on endothelial cell activation were inhibited by LY294002, a phosphatidylinositol 3-kinase inhibitor. In conclusion, bilirubin promotes angiogenesis through endothelial cells activation via Akt-eNOS-dependent manner.

Haeme oxygenase signalling pathway: implications for cardiovascular disease

Evidence now points to the haeme oxygenase (HO) pathway as a possible actor in modulating risk for cardiovascular disease (CVD). In particular, the HO pathway may represent a key endogenous modulator of oxidative, inflammatory, and cytotoxic stress while also exhibiting vasoregulatory properties. In this review, we summarize the accumulating experimental and emerging clinical data indicating how activity of the HO pathway and its products may play a role in mechanisms underlying the development of CVD. We also identify gaps in the literature to date and suggest future directions for investigation. Because HO pathway activity can be influenced not only by genetic traits and environmental stimuli but also by a variety of existing pharmacologic interventions, the pathway could serve as a prime target for reducing the overall burden of CVD. Further work is needed to determine the role of HO pathway products as possible prognostic markers of risk for clinical CVD events and the extent to which therapeutic augmentation or inhibition of HO pathway activity could serve to modify CVD risk.